How did so many writings of St. John Chrysostom survive?

We have an astonishing number of extant writings by St. John Chrysostom. One source says: > Chrysostom is among the most prolific of the Fathers: 17 treatises, more than 700 authentic homilies, commentaries on Matthew and on Paul (Letters to the Romans, Corinthians, Ephesians and Hebrews) and 241 letters are extant. He was not a speculative theologian. And I don't think I've ever encountered uncertainty about attribution. We're talking about someone who lived in the second half of the 4th century! How in the world do so many of his writings survive? Were they kept in a monastery/cathedral/library/etc.?